This invention relates to a tilt locking mechanism for marine propulsion devices and more particularly to an improved simplified tilt locking mechanism that permits the motor to be preset in a plurality of desired trim positions, which permits the motor to pop up under impact and return to position and also which is simple to operate and has a minimum of controls.
A wide variety of devices have been proposed for permitting the trim adjustment of an outboard drive such as the outboard drive unit of an inboard-outboard or an outboard motor per se. Many of these mechanisms also include a device that holds the outboard drive against popping up under reverse thrusts and which nevertheless permits the motor to pop up when traveling in a forward direction and when striking a submerged obstacle. Many of these systems employ hydraulic piston and cylinder arrangements for controlling the outboard drive position and/or movement. Although such hydraulic systems have a number of advantages, those which permit all of the required conditions to be met tend to be extremely complicated, expensive and cumbersome to operate.
In one of the more commonly used type of arrangements, a hydraulic cylinder and piston assembly is interposed between the outboard drive and the transom and embodies a shock absorbing valving arrangement so as to hold the outboard drive against reverse thrusts and also to permit it to pop up when an underwater obstacle is encountered. With such arrangements, the piston rod extends through one chamber of the hydraulic cylinder piston assembly and an arrangement must be employed to compensate for the changes in volume of the piston rod, depending upon the axial position of the associated piston. It is normally the practice to employ an inert gas acting over the hydraulic fluid so as to provide this compensation. Such arrangements, however, have a tendency to permit the inert gas to enter into the shock absorbing arrangement per se and thus significantly diminish the ability of the unit to resist reverse thrusts and absorb impacts.
It is, therefore, a principal object of this invention to provide an improved tilt locking mechanism for an outboard drive that employs a gas over oil arrangement and in which the gas cannot enter into the shock absorbing system.
It is a further object of this invention to provide a hydraulic shock absorbing assembly for an outboard drive using a gas accumulator to compensate for changes in volume of one of the shock absorbing chambers due to the use of a piston rod and in which the gas is effectively isolated from the shock absorbing arrangement.
In addition to employing a hydraulic shock absorbing arrangement for holding the outboard drive against reverse thrusts and for permitting it to pop up while traveling forwardly and striking a submerged obstacle with sufficient force, the hydraulic arrangements also may include a mechanism for permitting the outboard drive to be tilted up out of the water and held in a tilted up position. Such tilt locking mechanisms normally include a valve passage or passages that permit the chambers of the shock absorbing arrangement to communicate freely with each other without the restriction of the shock absorbing valves. These tilt locking valves are manually operated and normally require the operator to open the valve, manually tilt the motor up and subsequently to close the valve to lock the motor in a tilted up position. Of course, this necessitates the operator to use one hand to operate the valve and leaves only one hand free to manipulate the outboard drive.
It is, therefore, a further object of this invention to provide a simplified mechanism for locking an outboard drive in a tilted up position.
It is yet another object of this invention to provide a manual override for a hydraulic shock absorbing arrangement for an outboard drive that frees the operator's hands for moving the outboard drive to a tilted up position.